Ring rolling from metal blanks

ABSTRACT

A method of rolling a ring from a metal blank comprises mounting the blank ( 2 ) on a mandrel ( 4 ) between two forming rolls ( 6 ) located on opposite sides of the mandrel axis. A pair of lower growth control rolls ( 12 ) are located below and with their axes parallel to and on opposite sides of the mandrel axis ( 8 ), and a pair of upper growth control rolls ( 16 ) are arranged above and with their axes parallel and on opposite sides of the mandrel axis ( 8 ). The spacing between the pair of upper growth control rolls is different from that between the pair of lower growth control rolls. As the ring is rolled, both the forming rolls and the growth control rolls are engaged with it. In a modification of the method, the upper growth control rolls are replaced by a single roll ( 20 ) with its axis disposed directly over the mandrel axis.

This invention relates to the ring rolling of metal blanks. The blanksare typically of standard steels such as wrought steels, but couldcomprise other metals or alloys. They can be rolled to form rings havingmany uses, particularly bearing components. The invention may also beapplied to powder metal blanks.

In rolling processes of the kind described above, the metal blank ismounted on a mandrel located between two forming rolls either side ofthe mandrel axis. Growth control rolls are disposed above and below themandrel axis to engage the blank as it turns between the forming rolls.Four growth roll controls are used; one directly above another betweenthe mandrel axis and each forming roll. This process has produced goodresults with very good quality roundness in the final product. However,the process does generate lobes. The present invention seeks to furtherreduce the generation of lobes, and thereby further improve theroundness of the ring rolled product. According to the invention, thegrowth control rolls are arranged above, below and on either side of themandrel axis to generate a less symmetric pattern of forces acting onthe ring blank with more of the horizontal forces being resolved betweenthe upper or the lower growth control rolls and the forming rolls. Thepreferred arrangement has the pair of upper growth control rolls withtheir axes parallel to but closer than those of the lower rolls.However, for some applications of the invention the lower pair of growthcontrol rolls can be closer together than the upper pair.

In the method of the invention the upper and lower growth control rollswill normally be arranged with their axes equidistant on either side ofthe vertical plane containing the mandrel axis. In one variant of theinvention, the two upper growth controls can be replaced by a singlegrowth control with its axis disposed directly over the mandrel axis. Inthis variant, the upper growth control does of course apply onlyvertical forces to the ring blank with all the horizontal forces beingresolved between the lower growth control rolls and the forming rolls.The disposition of the growth control rolls is preferably selected tominimise the length of unsupported blank between peripherally adjacentrolls (forming rolls and growth control rolls).

In the methods of the invention, the mandrel axis and the forming rollsare in the same horizontal plane. However, in some applications of theinvention there can be some benefit in locating the mandrel axis belowthe axes of the forming rolls so that there is a vertical component ofthe forces between the forming rolls and the ring blank.

The invention will now be described by way of example and with referenceto the accompanying schematic drawings in which:

FIG. 1 shows a cross-section through ring rolling apparatus adapted topractice the method of the invention; and

FIG. 2 shows an alternative apparatus to that of FIG. 1 in which theupper growth controls are replaced by a single roll.

As shown in FIG. 1 a metal blank (2) is mounted on a mandrel (4)disposed between two forming rolls (6). The axis (8) of the mandrel (4)is located below the horizontal plane containing the axes (10) of theforming rolls, the line between the axis (8) and each forming roll axis(10) subtending an angle β with the horizontal. Angle β is normally nomore than 10°, and typically will be no more than 5°. Effectiveperformance has been achieved with angle β at around 1°.

Two lower growth control rolls (12) are disposed beneath the mandrel (4)to engage the metal blank (2) from below. The rolls (12) are arrangedsymmetrically on either side of the vertical plane containing themandrel axis (8); equally spaced from that vertical plane. The rolls(12) are mounted on a framework (14) enabling their spacing to beadjusted. It will be appreciated that the diameter of the lower growthcontrol rolls may need to vary depending upon the spacing between them,to avoid interference with either each other or the forming rolls. Thecritical factor is of course the line of engagement with the blank onthe mandrel, and the angle θ subtended between the line of engagementand the mandrel axis and the horizontal. This angle θ is typically inthe range of 50° to 70°, and normally at least 60°.

Two upper growth control rolls (16) are mounted in a framework (18) overthe mandrel axis for engaging the blank (2) from above. These rolls (16)are located closer to each other than are the lower growth control (12)but once again their spacing can be altered by movement of their axes inthe framework (18). The rolls (16) are also arranged symmetrically oneither side of the vertical plane containing the mandrel axis, and theangle θ′ subtended by the line of engagement of the roll (16) and theblank (2) and the mandrel axis relative to the horizontal will of coursebe greater than the angle θ defined in the location of the lower growthcontrols. The angle θ′ is typically in the range of 50° to 80°, normallyin the range 65° to 70°.

As noted above different sized growth control rolls can be useddepending upon the geometry of the desired roll arrangement and ofcourse the size of the ring to be rolled on the forming rolls. Becauseof the forces involved, the diameter of the growth control rolls shouldbe as much as the geometry allows. The location of the growth controlrolls relative to the blank is normally selected such that the spacingbetween the lines of engagement of the upper rolls (16) is substantiallyequal to the spacing between each upper roll and the line of engagementof the adjacent forming roll (6). The lower growth control rolls (12)are located in a similarly symmetric arrangement.

FIG. 2 shows a modification of the arrangement in FIG. 1 in which theupper growth control rolls (16) are replaced by a single roll (20). Inother respects the arrangement of forming and growth control rolls isthe same as in FIG. 1.

1. A method of rolling a ring from a metal blank, comprising mountingthe blank on a mandrel between two forming rolls located on oppositesides of the mandrel axis, with a pair of lower growth control rollslocated below and with their axes parallel to and on opposite sides ofthe mandrel axis, and a pair of upper growth control rolls arrangedabove and with their axes parallel and on opposite sides of the mandrelaxis, wherein the spacing between the pair of upper growth control rollsis different from the spacing between the pair of lower growth controlrolls; and rolling the ring between the forming rolls with the growthcontrol rings engaging the ring.
 2. A method according to claim 1wherein the spacing between the pair of upper growth control rolls isless than the spacing between the pair of lower growth control rolls. 3.A method according to claim 1, wherein the lower growth control rollsare located relative to the mandrel axis with their axes disposed at anangle in the range 50° to 70° below the horizontal plane containing themandrel axis.
 4. A method according to claim 3, when said angle is atleast 60°.
 5. A method according to claim 1, wherein the upper growthcontrol rolls are located relative to the mandrel axis with their axesdisposed at an angle in the range 50° to 80° above the horizontal planecontaining the mandrel axis.
 6. A method according to claim 5, whereinsaid angle is in the range 65° to 70°.
 7. (canceled)
 8. A methodaccording to claim 1, wherein the mandrel axis and the axes of theforming rolls are in the same horizontal plane.
 9. A method according toclaim 1, wherein the mandrel axis is disposed below a horizontal planecontaining the forming roll axes.
 10. A method according to claim 9,wherein the mandrel axis is disposed at an angle no greater than 10°below the horizontal plane containing the forming roll axes.
 11. Amethod according to claim 10, wherein the angle is no greater than 5°.12. A method of rolling a ring from a metal blank, comprising mountingthe blank on a mandrel between two forming rolls located on oppositesides of the mandrel axis, with a pair of lower growth control rollslocated below and with their axes parallel to and on opposite sides ofthe mandrel axis, and a single upper growth control roll arranged aboveand with its axis parallel and directly over the mandrel axis, androlling the ring between the forming rolls with the growth control ringsengaging the ring.
 13. A method according to claim 12, wherein the lowergrowth control rolls are located relative to the mandrel axis with theiraxes disposed at an angle in the range 50° to 70° below the horizontalplane containing the mandrel axis.
 14. A method according to claim 13,when said angle is at least 60°.
 15. A method according to claim 12,wherein the mandrel axis and the axis of the forming rolls are in thesame horizontal plane.
 16. A method according to claim 12, wherein themandrel axis is disposed below a horizontal plane containing the formingroll axes.
 17. A method according to claim 16, wherein the mandrel axisis disposed at an angle no greater than 10° below the horizontal planecontaining the forming roll axis.
 18. A method according to claim 17,wherein the angle is no greater than 5°.